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Lateral variation of major and trace elements in the Pliocene volcanic rock of the rock of the Northeast Japan.

日本东北部岩石上新世火山岩中主量元素和微量元素的横向变化。

基本信息

批准号：
02640592
负责人：
YASHIMA Ryuichi
金额：
$ 0.83万
依托单位：
Fukushima University.
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

It has been well-known that the Quaternary volcanic rocks increase gradually in alkali contents, especially in K_2O, other large ion lithophile elements (LIL elements), and high field strength elements (HFS elements) from the volcanic front toward the back-arc side across the NE Japan arc (Kuno, 1960; Kawano et al., 1961; Masuda, 1979; Fujimaki and Kurasawa, 1980; Fujitani and Masuda, 1981; Yoshida and Aoki, 1984; Sakuyama and Nesbitt, 1986; Nakagawa et al., 1988). More recently, several workers suggested the existence of the lateral variation of LIL elements including K, Rb and Sr of the volcanic rocks during the late Miocene time, based on the geochemical investigations of the Tertiary volcanic rocks from both the central Honshu and northern Honshu to southwest Hokkaido (Shuto et al., 1988; Tamura and Shuto, 1989; Okamura, 1987).In the NE Japan arc, the volcanic rocks formed by the Pliocene volcanism from 4 to 2 Ma show a widespread distribution which coincides roughly with that of the Quaternary volcanic rocks (Fig.1). We examined the abundances of major and trace elements for 111 rock samples from twelve Pliocene volcanic centers in the NE Japan arc. Based on these results and the published analyses, an across-arc compositional variation for the Pliocene volcanics will be examined in comparison with that for the Quaternary volcanics in the NE Japan arc.

众所周知，第四纪火山岩的碱含量逐渐增加，特别是K_2O、其他大离子亲石元素（LIL元素）和高场强元素（HFS元素）从火山前线沿日本东北弧向弧后侧逐渐增加（Kuno, 1960; Kawano et al., 1961; Masuda, 1979； Fujimaki和Kurasawa, 1980； Fujitani和Masuda, 1981； Yoshida和Aoki, 1984； Sakuyama和Nesbitt, 1986； Nakagawa等，1988）。最近，一些工作者根据本州中部和本州北部至北海道西南部第三纪火山岩的地球化学调查，提出了晚中新世时期火山岩中K、Rb、Sr等微量元素的横向变化（Shuto et al., 1988; Tamura and Shuto, 1989; Okamura, 1987）。在日本东北弧，4 ~ 2 Ma的上新世火山作用形成的火山岩分布广泛，与第四纪火山岩的分布大致一致（图1）。研究了日本东北弧12个上新世火山中心的111个岩石样品的主微量元素丰度。在此基础上，结合已发表的分析结果，对比分析了日本东北弧的上新世火山岩与第四纪火山岩的弧间成分变化。